Long description

enter underscore region colon

MOVE REGISTER coma hash 1 vertical line put a 1 in the register

XCHG REGISTER coma LOCK vertical line swap the contents of the register and lock variable

CMP REGISTER coma hash 0 vertical line was lock zero question mark

JNE enter underscore region vertical line if it was non zero coma lock was set coma so loop

RET vertical line return to caller semicolon critical region entered

leave underscore region colon

MOVE LOCK coma hash 0 vertical line store a 0 in lock

RET vertical line return to caller